234 TRANSACTIONS OF THE [May 18, 
II. Relations of Biceps to the adjoining deep ventro-appendic- 
ular muscles, viz.: the Coraco-humerals. 
III Relations of Biceps to the deep intrinsic flexor of the 
forearm, viz.: the Brachialus anticus. 
I. MorpHoLocy oF THE Biceps FLEXxoR CUBITT. 
We may in the first place consider the composition of the 
human Biceps in the light derived from the comparative study 
of the muscle in other vertebrates. 
Although our knowledge of comparative myology is still 
somewhat meagre, considering the extent of the subject, and al- 
though the results of investigations appear at times too frag- 
mentary and uncertain, yet enough is known to justify us in 
regarding the form in which the Biceps usually presents itself in 
man as the result of certain specializations of function acquired 
by the upper extremity, which have brought about a greater de- 
finition of certain portions, whereas other parts, lacking the 
stimulus of this functional requirement, have retrograded and 
have become toa great extent rudimentary or entirely elimin- 
ated. 
A. Origin. 
In the complete form the Biceps occupies two points of origin 
from the shoulder-girdle corresponding to the anterior edge of 
the glenoid socket and to the coracoid element. 
The actual arrangement of the muscle in individual forms 
will be naturally greatly influenced by the structure of the 
girdle, and notably by the predominance or reduction of the 
coracoid and its appendages. An instance of this is afforded 
by the extensive Coraco-radial muscle which represents the 
Biceps in Cryptobranchus japonicus, whereas, in many other 
forms, the coracoid origin of the muscle is much reduced or ab- 
sent, and the Biceps appears as arising solely from the glenoid 
margin. ; 
A glance at the arrangement in the vertebrate series will im- 
mediately indicate that the origin of the muscle is confined, 
strictly speaking, to the coracoid element of the pectoral girdle. 
It may arise by a single head, or, as in man, the origin may be 
double, hence the name. 
If, as in us, the coracoid is reduced and the scapula corre-_ 
spondingly increased, the muscle, ifit preserves its double origin, 
will arise by one head from the small coracoid process, by the 
other from that portion of the glenoid margin which is con- 
tributed by the coracoid bone. If the long tendon of the glenoid 
head of our Biceps is examined in subjects between the ages of 
